PARIS - Salty water just below the surface of Mars could hold enough oxygen to support the kind of microbial life that emerged and flourished on Earth billions of years ago, researchers reported Monday (Oct 22).
In some locations, the amount of oxygen available could even keep alive a primitive, multicellular animal such as a sponge, they reported in the journal Nature Geosciences.
"We discovered that brines" - water with high concentrations of salt - "on Mars can contain enough oxygen for microbes to breathe," said lead author Vlada Stamenkovic, a theoretical physicist at the Jet Propulsion Laboratory in California.
"This fully revolutionises our understanding of the potential for life on Mars, today and in the past," he told AFP.
Up to now, it had been assumed that the trace amounts of oxygen on Mars were insufficient to sustain even microbial life.
"We never thought that oxygen could play a role for life on Mars due to its rarity in the atmosphere, about 0.14 per cent," Stamenkovic said.
By comparison, the life-giving gas makes up 21 per cent of the air we breathe.
On Earth, aerobic - that is, oxygen breathing - life forms evolved together with photosynthesis, which converts CO2 into O2. The gas played a critical role in the emergence of complex life, notable after the so-called Great Oxygenation Event some 2.35 billion years ago.
But our planet also harbours microbes - at the bottom of the ocean, in boiling hot springs - that subsist in environments deprived of oxygen.
"That's why - whenever we thought of life on Mars - we studied the potential for anaerobic life," Stamenkovic.
LIFE ON MARS?
The new study began with the discovery by Nasa's Curiosity Mars rover of manganese oxides, which are chemical compounds that can only be produced with a lot of oxygen.
Curiosity, along with Mars orbiters, also established the presence of brine deposits, with notable variations in the elements they contained.
A high salt content allows for water to remain liquid - a necessary condition for oxygen to be dissolved - at much lower temperatures, making brines a happy place for microbes.
Depending on the region, season and time of day, temperatures on the Red Planet can vary between minus 195 and 20 deg C.
The researchers devised a first model to describe how oxygen dissolves in salty water at temperatures below freezing.
A second model estimated climate changes on Mars over the last 20 million years, and over the next 10 million years.
Taken together, the calculations showed which regions on the Red Planet are most likely to produce brine-based oxygen, data that could help determine the placement of future probes.
"Oxygen concentrations (on Mars) are orders of magnitude" - several hundred times - "greater than needed by aerobic, or oxygen-breathing - microbes," the study concluded.Fergalicious Women's Freelove Ballet Flat Doe Size 5.0DANSKO WOMEN'S ANN SLIP-ON ELASTIC SHOES BLACK LEATHER 40 10 MEDIUM $145 , Munro American Brown Leather and Fabric Oxford Loafers Size 6 1/2 NSperry Top Sider Womens Size 6 Slip On Boat Loafer White Navy & Brown , Bogs Stewart Clogs - Women's Size 6, Black , Genuine Leather Womens Brown SAS Simplify Loafer Style Shoes - Size US 10.5W , Aetrex E261 Maggie Slip On Suede Women’s Size 7 Wide New In BoxWomen's Naturalizer N5 contour ortholite Freeda black slip-on Size 10M , Drew Women's Black Leather Mary Jane Therapeutic Diabetic Walking Shoe US 11 N , Women's Privo by Clarks Loafers Shoes Size 7.5M Brown Suede Orange Strapped T2 , J/SLIDES AZTEC FASHION SNEAKER sz 7.5 PEWTER LEATHERAlegria Women's Black Patent Leather Buckle Strap Size-40 , Keds Women's Burgandy CH Ox Sneakers Shoes Ret $45 NewGeox Blue Suede Trainers Size 40EU/9USDearfoams Men's Mesh Thong Slipper , Women's"JUICE COUTURE"Fashion Logo Sport Sneakers Walking Shoes size 7.5M Cute!Women's NIKE Running Barefoot Ride Size 6.5Womens skechers gowalk 3 Goga Pillars Shoes Sz 8Grasshoppers by Keds Casual Sneakers,Red Hat Society,#EH13653, White/Red,Women 9 , Skechers Shape Ups Shoes Sz 7.5 Women Toning Fitness Exercise Walk Sneaker 12320 , Nike REAX RUN 8 SHOES WOMENS SIZE 8Puma Womens Fierce evoKNIT Gray Fashion Sneakers 9.5 Medium (B,M) BHFO 5428 , K1X WMNS Shorty H1TOP LE women lifestyle casual shoes NEW bright blue blackWomen's WOMEN REEBOK BLACK PRINCESS 7344 Low-priced Athletic ShoesChung-Shi Sensomo IV Loafer - Womens Slip-Ons, 40 Euro (US women 8.5)NIKE AIR ZOOM FITNESS SIZE 9 WOMEN'S RUNNING TRAINING (904645 103) , Cole Haan Womens W05485 Green Fashion Sneaker Size 6 (4920)RARE WOMEN'S 2007 NIKE VANDAL LOW Shoes Buff, Green & Pink Size 9.5 , New Mizuno Wave Daichi 2 Women's Hiking Trail Running Shoes, Size 6, J1GD177103 , CLARKS BLACK LEATHER WATERPROOF SNEAKERS WALKING DUCK BOOTS SHOES WOMENS SZ 6 M ,
"Our results do not imply that there is life on Mars," Stamenkovic cautioned. "But they show that the Martian habitability is affected by the potential of dissolved oxygen."